Concrete is produced by mixing cementitious material, water, aggregates (such as gravel, crushed limestone, or sand) into a plastic mixture, which undergoes a chemical process (known as hydraulic curing) to harden and strengthen. Other materials, such as admixtures, pozzolans, plasticizers, reinforcers or other compounds, may be added to the mix, depending on the concrete formula selected. Concrete formulas are grouped into concrete families, which are characterized by similarities in composition and function, and for which a reliable relationship between relevant properties can be determined. For example, a concrete family may be defined by concrete formulas sharing type or source characteristics (e.g., Portland pozzolan cement, masonry cement, blends, etc.); demonstrably similar aggregates or admixtures; the use and type of plasticizers or other water-reducing compounds; consistence (or slump) classes; entrained air content; mixing and curing methods; or combinations of these various qualities or categories. Particular concrete families are desired for various applications, based upon the performance and cost constraints of the end use.
Each concrete family is characterized by a relationship between various relevant material design properties. For concrete, such properties include among others the water-cement ratio (W/C ratio), which is the ratio of water mass to cement mass (including pozzolanic materials, if used) in the mixture, the compressive strength, the tensile strength, elasticity, and thermal expansion coefficient. For example, in a particular concrete family, the W/C ratio is inversely related to the compressive strength. However, the particular nature of that inverse relationship is influenced by other characteristics inherent to the concrete family.
Although the general relationship between W/C ratio and compressive strength in concrete is known, builders and concrete producers have been unable to quickly and accurately determine the water and concrete amounts for a particular delivery of concrete. In current practice, the concrete production process consists of a series of automated and manual steps that may result in an inaccurate record of exactly how much water and cement actually went into the delivery. Also, trucks delivering concrete to a construction site may add varying amounts of water to the mixture it is transporting. Because this will alter the W/C ratio of each individual mixture transported to the site, the resulting concrete pour may exhibit inadequate strength properties unless corrected. Current practice is to use more cementitious material in the concrete formula mixed at the plant to compensate for water that may be added during transport. However, because cementitious material is generally the most expensive component of concrete, this has the effect of increasing cost. Furthermore, if substantial quantities of water must be added to the delivered concrete during transport or pouring, the resulting concrete may still exhibit inadequate strength. Concrete exhibiting inadequate compressive strength must be removed and reworked, resulting in substantial time delays and cost overruns. Because concrete is not considered fully cured and of maximum strength until twenty-eight days after pouring, the resulting delay may be very substantial, and replacement of the defective concrete can be very expensive and require reworking of other parts of the construction.
What is needed, then, is a concrete production method and system for quickly and accurately determining water and concrete inputs in order to determine an expected compressive strength for the cured concrete.